Conventionally, a surface light apparatus that uses a plurality of light emitting diodes (“LEDs”) as point light sources is known as an illuminating means for a liquid crystal monitor used in a personal computer, television and so on.
The surface light source apparatus arranges a plurality of LEDs in a matrix shape on the back surface of a flat light flux controlling member having virtually the same shape as a liquid crystal panel of a liquid crystal display monitor. The surface light source apparatus allows light emitted from the LEDs to be incident inside the light flux controlling member, and controls the traveling direction of light when emitting light from the light flux controlling member. Then, the surface light source apparatus diffuses light emitted from the light flux controlling member by a light diffusing member, and then planarly illuminates the liquid crystal display panel from the back.
Patent Literature 1 discloses a planar light source from which light having transmitted through an optical element is emitted virtually vertically with respect to the plane surface. FIG. 1 schematically shows a surface light source apparatus that uses as light sources the LEDs disclosed in Patent Literature 1. As shown in FIG. 1, in surface light source apparatus 100, micro lens arrays 102 are arranged to meet a plurality of LEDs 101 on a one-by-one basis. Micro lens arrays 102 control the traveling directions of light emitted from LEDs 101, so that surface light source apparatus 100 emits light in the direction vertical to the plane surface of the substrate (i.e. upward).
Patent Literature 2 discloses a display apparatus in which a hollow part is formed inside a convex part of a lens case and in which void parts with inclining surfaces which reflect light emitted in the horizontal direction from a light emitting element, toward the convex parts, are formed outside the outer periphery of the hollow part.
FIG. 2 is a configuration diagram showing a display apparatus disclosed in Patent Literature 2. As shown in FIG. 2, matrix display apparatus 130 aligns light emitting elements 132 in a matrix shape, on display panel substrate 131, and arranges lens cases 133 on the side of the surface of light emitting elements 132. Lens case 133 is mounted on display panel substrate 131 to be closely attached. In lens case 133, convex part 134 of virtually a semispherical shape is formed in the position meeting light emitting element 132, and hollow part 135 that includes light emitting element 132 inside convex part 134 is formed. The sidewalls of hollow part 135 takes in light emitted from light emitting element 132 by refracting the light such that the light travels toward the front side (i.e. upward in FIG. 2). The sidewalls of hollow part 135 are only the incidence planes for light emitted from light emitting element 132. Further, in lens case 133, void parts 136 are formed around hollow part 135 that includes light emitting element 132. Void parts 136 totally reflect light emitted in the horizontal direction from light emitting element 132 and taken in by lens case 133, toward the front side through inclining surfaces 137 of void parts 136 and insulating substrate 138. By this means, the luminance of illumination light in the front side of matrix display apparatus 130 increases.
Citation List
Patent Literature
Patent Literature 1: Japanese Patent Application Laid-Open No. 2002-49326
Patent Literature 2: Japanese Patent Application Laid-Open No. 2001-250986